Java and Python FTP Attacks Can Punch Holes Through Firewalls

“The Java and Python runtimes fail to properly validate FTP URLs, which can potentially allow attackers to punch holes through firewalls to access local networks,” reports CSO Online. itwbennett writes: Last weekend security researcher Alexander Klink disclosed an interesting attack where exploiting an XML External Entity vulnerability in a Java application can be used to send emails. At the same time, he showed that this type of vulnerability can be used to trick the Java runtime to initiate FTP connections to remote servers. After seeing Klink’s exploit, Timothy Morgan, a researcher with Blindspot Security, decided to disclose a similar attack that works against both Java’s and Python’s FTP implementations. “But his attack is more serious because it can be used to punch holes through firewalls,” writes Lucian Constantin in CSO Online. “The Java and Python developers have been notified of this problem, but until they fix their FTP client implementations, the researcher advises firewall vendors to disable classic mode FTP translation by default…” reports CSO Online. “It turns out that the built-in implementation of the FTP client in Java doesn’t filter out special carriage return and line feed characters from URLs and actually interprets them. By inserting such characters in the user or password portions of an FTP URL, the Java FTP client can be tricked to execute rogue commands…”


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